U.S. patent application number 12/841152 was filed with the patent office on 2011-04-07 for method for transmitting power headroom report and buffer status report in a wireless communication system and related communication device.
Invention is credited to Chia-Chun Hsu.
Application Number | 20110080881 12/841152 |
Document ID | / |
Family ID | 42797123 |
Filed Date | 2011-04-07 |
United States Patent
Application |
20110080881 |
Kind Code |
A1 |
Hsu; Chia-Chun |
April 7, 2011 |
METHOD FOR TRANSMITTING POWER HEADROOM REPORT AND BUFFER STATUS
REPORT IN A WIRELESS COMMUNICATION SYSTEM AND RELATED COMMUNICATION
DEVICE
Abstract
A method for transmitting a power headroom report (PHR) and a
buffer status report (BSR) for a user equipment in a wireless
communication system includes triggering a BSR when a triggering
event for the BSR occurs, for reporting a status of an uplink
transmission buffer of the user equipment to a network of the
wireless communication system, checking whether the BSR is
triggered for reporting that the uplink transmission buffer is
empty, when the BSR is triggered for reporting that the uplink
transmission buffer is empty, checking whether a PHR is triggered
and whether there is room for the PHR in an uplink resource
according to a priority order, and generating the PHR and
transmitting the PHR instead of the BSR to the network when the PHR
is triggered and there is not enough room for the PHR in the uplink
resource.
Inventors: |
Hsu; Chia-Chun; (Taoyuan
County, TW) |
Family ID: |
42797123 |
Appl. No.: |
12/841152 |
Filed: |
July 21, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61247579 |
Oct 1, 2009 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 52/365
20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 24/10 20090101
H04W024/10 |
Claims
1. A method for transmitting a power headroom report (PHR) and a
buffer status report (BSR) for a user equipment in a wireless
communication system, the method comprising: triggering a BSR when
a triggering event for the BSR occurs, for reporting a status of an
uplink transmission buffer of the user equipment to a network of
the wireless communication system; checking whether the BSR is
triggered for reporting that the uplink transmission buffer is
empty; when the BSR is triggered for reporting that the uplink
transmission buffer is empty, checking whether a PHR is triggered
and whether there is room for the PHR in an uplink resource
according to a priority order; and when the PHR is triggered and
there is not enough room for the PHR in the uplink resource,
generating the PHR and transmitting the PHR instead of the BSR to
the network.
2. The method of claim 1, wherein the PHR transmitted instead of
the BSR comprises one bit for indicating whether the BSR reports
the empty uplink transmission buffer.
3. The method of claim 1 further comprising: when no PHR is
triggered, generating the BSR and transmitting the BSR to the
network, for reporting that the uplink transmission buffer is
empty.
4. The method of claim 1 further comprising: when the PHR is
triggered and there is enough room for the PHR in the uplink
resource, generating the BSR and PHR; and transmitting the BSR and
PHR to the network.
5. The method of claim 1, wherein the priority order that the user
equipment follows to check whether there is room for the PHR in the
uplink resource indicates that the BSR is prior than the PHR.
6. The method of claim 1, wherein the BSR and PHR are Medium Access
Control (MAC) control elements.
7. A communication device of a wireless communication system for
transmitting a power headroom report (PHR) and a buffer status
report (BSR), the communication device comprising: means for
triggering a BSR when a triggering event for the BSR occurs, for
reporting a status of an uplink transmission buffer of the
communication device to a network of the wireless communication
system; means for checking whether a PHR is triggered when the BSR
is triggered for reporting that the uplink transmission buffer is
empty; means for checking whether there is room for the PHR in an
uplink resource according to a priority order when the BSR is
triggered for reporting that the uplink transmission buffer is
empty and the PHR is triggered; and means for generating the PHR
and transmitting the PHR instead of the BSR to the network when the
PHR is triggered and there is not enough room for the PHR in the
uplink resource.
8. The communication device of claim 7, wherein the PHR transmitted
instead of the BSR comprises one bit for indicating whether the BSR
reports the empty uplink transmission buffer.
9. The communication device of claim 7 further comprising: means
for generating the BSR and transmitting the BSR to the network when
no PHR is triggered, for reporting that the uplink transmission
buffer is empty.
10. The communication device of claim 7 further comprising: means
for generating the BSR and PHR when the PHR is triggered and there
is enough room for the PHR in the uplink resource; and means for
transmitting the BSR and PHR to the network.
11. The communication device of claim 7, wherein the priority order
that the communication device follows to check whether there is
room for the PHR in the uplink resource indicates that the BSR is
prior than the PHR.
12. The communication device of claim 7, wherein the BSR and PHR
are Medium Access Control (MAC) control elements.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/247,579, filed on Oct. 1, 2009 and entitled
"METHOD AND APPARATUS FOR PHR replacing a empty BSR IN A WIRELESS
COMMUNICATIONS SYSTEM", the contents of which are incorporated
herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method for transmitting a
power headroom report and a buffer status report for a user
equipment in a wireless communication system and related
communication device, and more particularly, to a method for
transmitting a power headroom report and a buffer status report
according to a status of an uplink transmission buffer of a user
equipment and related communication device.
[0004] 2. Description of the Prior Art
[0005] A long-term evolution (LTE) system, initiated by the third
generation partnership project (3GPP), is now being regarded as a
new radio interface and radio network architecture that provides a
high data rate, low latency, packet optimization, and improved
system capacity and coverage. In the LTE system, an evolved
universal terrestrial radio access network (E-UTRAN) includes a
plurality of evolved Node-Bs (eNBs) and communicates with a
plurality of mobile stations, also referred as user equipments
(UEs). The LTE radio protocol stack includes the Layer 3, also
known as the Radio Resource Control (RRC) layer, the Layer 2,
consisting of three sub-layers that are the Packet Data Convergence
Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the
Medium Access Control (MAC) layer, and the Layer 1, also known as
the Physical (PHY) layer.
[0006] A dynamic scheduling function is used in the UE MAC layer
and the eNB MAC layer for utilizing shared channel (SCH) resources.
For uplink (UL), an eNB allocates an UL resource to an UE through a
physical downlink control channel (PDCCH) signaling. In order to
utilize SCH resources more efficiently, a semi-persistent
scheduling (SPS) function is further introduced in the LTE system
for serving upper layer applications that generate semi-static size
data periodically, e.g. VoIP services. The eNB activates SPS
resources by sending a PDCCH signaling, and after the SPS
activation, SPS resources are periodically allocated to the UE
without being through the PDCCH signaling.
[0007] According to the UE MAC specification, a Buffer Status
Report (BSR) provides the serving eNB with information about the
amount of data available for transmission in an UL transmission
buffer of the UE. The BSR is one of MAC control elements included
in a MAC Protocol Data Unit (PDU). There are three types of BSRs,
regular BSR, periodic BSR and padding BSR, caused by different
triggering events. The regular BSR is triggered when UL data which
belongs to a logical channel with higher priority than those for
which data already existed in the transmission buffer arrives at
the transmission buffer, when a serving cell change occurs, or when
a retransmission BSR timer expires and the UE has data available
for transmission. The padding BSR is triggered when UL resources
are allocated and the number of padding bits is equal to or greater
than the size of a BSR MAC control element. The periodic BSR is
triggered when a periodic BSR timer expires, and is used for
providing the eNB with updated status of the UE transmission buffer
periodically. The regular BSR, the periodic BSR, and the padding
BSR are reported by different formats including long BSR, short
BSR, and truncated BSR.
[0008] In addition, a Power Headroom Report (PHR) provides the
serving eNB with information about the difference between the
nominal UE maximum transmit power and the estimated power for
UL-SCH transmission, which is also one of MAC control elements
included in a MAC PDU. Please refer to FIG. 1, which is a diagram
illustrating the format of a PHR MAC control element according to
the prior art. The PHR MAC control element consists of 2-bit "R"
field for reserved bits and 6-bit "PH" field indicating power
headroom level. Each reserved bit is set to 0.
[0009] The PHR is triggered when a prohibit PHR timer expires and
the path loss has changed more than a specific value since the last
transmission of a PHR when the UE has UL resources for new
transmission, and is also triggered when a periodic PHR timer
expires. When the UE has UL resources allocated for new
transmission in the current TTI, and at least one PHR has been
triggered since the last transmission of a PHR, and the allocated
UL resources can accommodate a PHR MAC control element, the UE MAC
layer obtains the value of the power headroom from the UE PHY
layer, generates a PHR MAC control element based on the value
reported by the UE PHY layer, and instructs the UE PHY layer to
transmit the PHR MAC control element. Based on the received PHR,
the eNB adaptively selects a modulation and coding scheme (MCS) for
the UE, and therefore the UE is able to use an appropriate data
rate to transmit data for higher transmission efficiency. According
to the current MAC specification, the UE MAC layer performs logical
channel prioritization to generate a MAC PDU, and the BSR MAC
control element has higher priority than the PHR MAC control
element.
[0010] Note that, when SPS is configured, BSRs are necessary to
quickly signal to the eNB the possible occurrence of data that has
lower priority than SPS data in the UL transmission buffer.
However, BSRs do not help in quickly adapting the MCS for the UE,
which is achieved through PHRs. In the case of SPS data
transmission, such as VoIP transmission, the transport block size
agreed for the E-UTRAN allows a short BSR or a PHR to be
transmitted. For VoIP transmission, with every new speech frame, a
regular BSR is triggered and sent in an UL resource, and most of
BSRs report empty buffer, referred as empty BSRs.
[0011] Based on that the BSR has higher priority than the PHR, with
every speech frame, no PHR can be sent without segmentation or
delay even the BSR reports empty UL transmission buffer; however,
the empty BSR seems less important than the PHR. In this situation,
the eNB may lose the opportunity to adapt the MCS for the UE
promptly due to the late PHR even no PHR. Furthermore, when the UE
decides not to segment the VoIP packet by considering logical
channel prioritization, the PHR is delayed for a long time, which
also decreases transmission efficiency. Therefore, in order to have
efficient transmission, it is important for the UE to send the BSR
and the PHR when they are surely required.
SUMMARY OF THE INVENTION
[0012] The present invention therefore provides a method for
transmitting a PHR and a BSR for a UE in a wireless communication
system and related communication device.
[0013] According to one aspect of the present invention, a method
for transmitting a PHR and a BSR for a UE in a wireless
communication system includes triggering a BSR when a triggering
event for the BSR occurs, for reporting a status of an UL
transmission buffer of the UE to a network of the wireless
communication system, checking whether the BSR is triggered for
reporting that the UL transmission buffer is empty, checking
whether a PHR is triggered and whether there is room for the PHR in
an UL resource according to a priority order when the BSR is
triggered for reporting that the UL transmission buffer is empty,
and generating the PHR and transmitting the PHR instead of the BSR
to the network when the PHR is triggered and there is not enough
room for the PHR in the UL resource.
[0014] According to another aspect of the present invention, a
communication device of a wireless communication system for
transmitting a PHR and a BSR includes means for triggering a BSR
when a triggering event for the BSR occurs, for reporting a status
of an UL transmission buffer of the communication device to a
network of the wireless communication system, means for checking
whether a PHR is triggered when the BSR is triggered for reporting
that the UL transmission buffer is empty, means for checking
whether there is room for the PHR in an UL resource according to a
priority order when the BSR is triggered for reporting that the UL
transmission buffer is empty and the PHR is triggered, and means
for generating the PHR and transmitting the PHR instead of the BSR
to the network when the PHR is triggered and there is not enough
room for the PHR in the UL resource.
[0015] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagram illustrating the format of a PHR MAC
control element according to the prior art.
[0017] FIG. 2 is a schematic diagram of a wireless communication
system.
[0018] FIG. 3 is a schematic diagram of a communication device
according to an example of the present invention.
[0019] FIG. 4 is a flowchart of a process according to an example
of the present invention.
[0020] FIG. 5 is a diagram illustrating the format of a PHR MAC
control element according to an example of the present
invention.
DETAILED DESCRIPTION
[0021] Please refer to FIG. 2, which is a schematic diagram of a
wireless communication system 10. The wireless communication system
10 can be a long-term evolution (LTE) system or a system of a
further release version, such as an LTE-Advanced system, or other
mobile communication systems. The wireless communication system 10
is briefly composed of a network and a plurality of user equipments
(UEs), as the structure illustrated in FIG. 2. In the LTE system,
the network is referred as an evolved universal terrestrial radio
access network (E-UTRAN) comprising a plurality of evolved base
stations (eNBs). The UEs can be devices such as mobile phones,
computer systems, etc. Besides, the network and the UE can be seen
as a transmitter or receiver according to transmission direction,
e.g., for uplink (UL), the UE is the transmitter and the network is
the receiver, and for downlink (DL), the network is the transmitter
and the UE is the receiver.
[0022] Please refer to FIG. 3, which is a schematic diagram of a
communication device 20 according to an example of the present
invention. The communication device 20 can be the UE shown in FIG.
2 and includes a processing means 200 such as a microprocessor or
ASIC, a memory unit 210, and a communication interfacing unit 220.
The memory unit 210 may be any data storage device that can store
program code 214 for access by the processor 200. Examples of the
memory unit 210 include but are not limited to a subscriber
identity module (SIM), read-only memory (ROM), random-access memory
(RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data
storage devices. The communication interfacing unit 220 is
preferably a radio transceiver for wirelessly communicating with
the network.
[0023] Please refer to FIG. 4, which is a flowchart of a process 40
according to an example of the present invention. The process 40 is
utilized for transmitting a power headroom report (PHR) and a
buffer status report (BSR) for the MAC layer of a UE in the
wireless communication system 10. Through the process 40, the UE
transmits the PHR and the BSR when they are really required for the
eNB, such that the modulation and coding scheme (MCS) is adapted in
time. The process 40 can be compiled into the program code 214. The
process 40 includes the following steps:
[0024] Step 400: Start.
[0025] Step 402: When a triggering event for a BSR occurs, trigger
the BSR.
[0026] Step 404: Check whether the BSR is triggered for reporting
that the UL transmission buffer is empty. When the BSR is triggered
for reporting the empty UL transmission buffer, perform Step 406;
else, perform Step 416.
[0027] Step 406: Check whether a PHR is triggered. When the PHR is
triggered, perform Step 408; else, perform Step 412.
[0028] Step 408: Check whether there is room for the PHR in an UL
resource. When there is not enough room for the PHR in the UL
resource, perform 410; else, perform Step 414.
[0029] Step 410: Generate the PHR and transmit the PHR instead of
the BSR to the eNB.
[0030] Step 412: Generate the BSR and transmit the BSR to the
eNB.
[0031] Step 414: Generate the BSR and the PHR, and transmit the BSR
and PHR to the eNB.
[0032] Step 416: End.
[0033] Note that the present invention does not redefine triggering
events of the BSR and the PHR, which are the same with the current
3GPP MAC specification and are not given herein. Step 402 is a
conventional step as in the prior art. According to Step 402, when
a triggering event for the BSR occurs, the UE triggers the BSR for
reporting a status of an UL transmission buffer, which indicates
the size of the data available to be transmitted in the UL
transmission buffer, to the eNB. According to Step 404, when the
BSR is triggered, the UE checks whether the BSR is triggered for
reporting that the UL transmission buffer is empty, and then
performs Step 406 or Step 416 according to the status of the UL
transmission buffer. When the UE detects that the BSR is not
triggered for the empty UL transmission buffer, in other words, the
BSR is triggered for the data available for transmission in the UL
transmission buffer, the BSR is valuable for the eNB for allocating
UL resources. In this situation, the UE leaves the process 40 and
transmits the BSR as the UE does in the prior art in which the BSR
is of higher priority.
[0034] On the other hand, when the UE detects that the BSR is
triggered for reporting the empty UL transmission buffer, according
to Step 406, the UE further checks whether a PHR is triggered. This
is because the PHR is regarded as more important than the BSR
reporting empty UL transmission buffer, which the eNB does not need
to know about. The UE further performs Step 408 or Step 412
according to whether the PHR is triggered. When the UE detects no
PHR is triggered, according to Step 412, the UE only generates the
BSR and transmits the BSR, for reporting the empty UL transmission
buffer to the eNB.
[0035] When the UE detects that the PHR is triggered, which implies
that the UE intends to report both the empty BSR and the PHR,
according to Step 408, the UE further checks whether there is
enough room for the PHR to be transmitted in an UL resource, and
performs Step 410 or Step 414 accordingly. Please note that, the UE
follows a priority order that prioritizes the BSR than the PHR, as
the priority order in the prior art, to check if there is enough
room for the PHR in the UL resource. When the UE detects there is
enough room for the PHR in the UL resource, which implies that the
UL resource is large enough to transmit both of the BSR reporting
the empty UL transmission buffer and the PHR, according to the Step
414, the UE generates the BSR and the PHR, and transmits the BSR
and PHR through the UL resource to the eNB.
[0036] On the other hand, when the UE detects that there is not
enough room for the PHR, the UE generates the PHR and transmits the
PHR instead of the BSR. The UE only transmits the PHR and does not
transmit the empty BSR because the PHR is more important than the
empty BSR that is unnecessary for the eNB. Therefore, the PHR
transmission is not segmented or delayed, and the eNB is able to
adapt the MCS of the UE promptly according to the reported PHR, so
that the transmission efficiency is improved.
[0037] Step 404, Step 406, Step 408, and Step 410 implement the
main idea of the present invention that is to transmit the PHR
instead of the BSR when the BSR is triggered for reporting the
empty UL transmission buffer. The process 40 can be used when
dynamic scheduling or semi-persistent scheduling (SPS) is
configured, and is more beneficial to the condition when SPS is
configured because most of the time the UE transmits all SPS data,
e.g. VoIP data available in the UL transmission buffer through the
SPS resource and left the UL transmission buffer empty. Through the
process 40, UL resources used for transmitting unnecessary empty
BSRs are reduced and PHRs have chances to be sent instead.
[0038] The BSR and the PHR are MAC control elements. The PHR that
replaces the empty BSR has different formats. One format is as the
prior art shown in FIG. 1; by this format, the eNB receives the PHR
without any information related to the empty UL transmission
buffer. Please refer to FIG. 5, which is a diagram illustrating the
format of a PHR MAC control element according to an example of the
present invention. Idea of the format shown in FIG. 5 is using one
bit of the PHR to indicate whether the BSR reports the empty UL
transmission buffer. As shown in FIG. 5, the PHR MAC control
element consists of 1-bit "R" field for a reserved bit, 1-bit "T"
field indicating whether the BSR reports the empty UL transmission
buffer, and 6-bit "PH" field indicating power headroom level. The
"T" field is set to be identical to the "R" field to indicate that
the PHR is independent of the BSR, which implies that the BSR is
also transmitted. The "T" field is set to be different from the "R"
field to indicate the empty BSR. For example, when the eNB receives
a PHR with the "R" field set to 0 and the "T" field set to 1, the
eNB recognizes that the UL transmission buffer is empty according
to the "T" field of the PHR.
[0039] Please note that the abovementioned steps of the process 40
can be realized by means that could be hardware, firmware known as
a combination of a hardware device and computer instructions and
data that reside as read-only software on the hardware device, or
an electronic system. Examples of hardware can include analog,
digital and mixed circuits known as microcircuit, microchip, or
silicon chip. Examples of the electronic system can include system
on chip (SOC), system in package (Sip), computer on module (COM),
and the communication device 20.
[0040] In conclusion, according to the present invention, the UE
transmits the PHR instead of the BSR when the BSR is triggered for
reporting an empty UL transmission buffer, so that the eNB has
chances to adapt the MCS of the UE in time according to the
reported PHRs. Therefore, the transmission efficiency is
enhanced.
[0041] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
* * * * *